• Proceedings of the Korean Magnestics Society Conference
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• 2015.05a
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• pp.84-85
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• 2015

• Proceedings of the Korean Magnestics Society Conference
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• 2013.12a
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• pp.13-14
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• 2013

• Proceedings of the Korean Magnestics Society Conference
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• 2016.05a
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• pp.13-14
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• 2016

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.1
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• pp.8-15
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• 1999

In order to develop an effective way of measuring the mode I stress intensity factor, $K_I$, by the technique based on the alternating current potential drop (ACPD), the effect of the magnetic flux in the air on the change in potential drop due to load for both ferromagnetic and paramagnetic materials containing a two-dimensional surface crack was investigated. Additionally the effects of the demagnetization and the crack length on the change in potential drop were examined. In the case that the measuring system was designed to induce a large amount of electromotive force, the amount of the change in potential drop due to load was shown to increase largely Also the relationship between the change in potential drop and that in $K_I$ was indicated to be linear without any treatment and it was shown that the demagnetization had almost no effect on the change in potential drop. The change in potential drop did not depend on the crack length but on the measuring system. For the application of the ACPD technique to determine $K_I$.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.1109-1112
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• 2015

A milatary ship without degaussing coil has a vertical magnetization to compensate magnetization induced by the vertical magnetic field component of earth magnetic field during demagnetization process. Flash D is very useful to acquire vertical magnetization. However this is hard to predict vertical magnetization. This experiment was investicated on another method, which used the only vertical bias magentic field. The specimens were prepared by thin Zn coated steel sheet with a thickness of 0.15mm. The shapes of 3 specimes was rectangular, triangular and circular cylinders. These shapes were corresponded to the shapes of bow, mid and stern of a vessel. Through FEM analysis, the difference of magnetic signatures for these specimens was recognized and the residual magnetization curve was measured. magnetic field was generated by a solenoid coil and magnetic signature was measured by a magnetic field sensor. A linearity between a vertical bias magnetic field and a vertical manetzation existed and the vertical magnetization of a miltary vessel was predicted by the linearity.

• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.5
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• pp.585-590
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• 2014

A permanent vertical magnetization should be obtained to counteract induced vertical magnetization due to the earth's background field during the Flash D demagnetization process. A vertical susceptibility is needed to calculate a extra-permanent magnetization, which is needed to control the permanent vertical magnetization in stage 2 of Flash D demagnetization and added to the final vertical permanent magnetization. Two susceptibilities were found in this paper. One is obtained from the extra-magnetization. The other is obtained by magnetic field measurement from the scaled physical vessel when the vessel is excited by vertical magnetic field. The initial susceptibility by the extra-magnetization was 0.101~0.109 and the one from the measured magnetic field was 0.122. Two susceptibilities have a good agreement each other. From this paper, it is found that the susceptibility is able to appllied to calculate the extr-magnetization.

• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.24-28
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• 2009

In this study, we investigated whether the anhysteretic demagnetization process would be applicable to remove a complicated magnetization of a steel tube as a part of the experimental earlier study for a deperming of naval vessel. The magnetic tube used in this study was a 10cm-long and 1cm-diameter steel tube, and magnetized with a E-shape ferrite core to form a nonuniform magnetization in it. In the anhysteretic demagnetization process, a dc magnetic field applied along the longitudinal direction of the tube decreased from ${\pm}$3kA/m to zero-field with the step of ${\pm}$300A/m. At the same time, an ac bias magnetic field with the frequency of 60Hz and the field intensity of 300A/m was excited along the circumstantial direction of the tube. It was found that the anhysteretic process was useful to demagnetize a small-object like a steel tube from the experimental results showing the residual magnetization reduced over 90%.

• Electrical & Electronic Materials
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• v.3 no.1
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• pp.36-44
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• 1990

본 연구는 34wt%(5Ce-Didymium)-Fe-1wt%B 합금의 분말입도, 성형압력 및 소결온도 에 따른 자기적 성질에 관하여 연구하였다. 그리고 각각의 자기적 성질에 영향을 주는 인자를 알아내기 위하여 밀도측정, 미세조직 및 자구를 관찰하였다. 미세조직은 금속현미경을 이용하여 관찰하였으며 자구는 Bitter법으로 관찰하였다. 결과는 아래와 같다. (1)분말의 입도와 결정립 크기가 작아질수록 경질자기 특성은 증가하였으며 소결온도가 증가할수록 경질자기 특성도 증가하였다. 그러자 압력은 1000kg/$cm^{2}$일때 가장 좋은 경질자기 특성이 얻어졌다. (2)결정립이 클수록 자구의 구조는 복잡했으며 미세한 결정립일수록 큰 결정립에 비해 큰 보자력을 갖는다. 포화된 후에는 거의 모든 결정립이 단자구였으며 열적으로 탈자되었을 경우에는 모두가 multi-domain였다. (3)가장 우수한 경질자기 특성은 3-5.mu.m의 분말을 사용하여 1080.deg.C에서 소결한 후 590.deg.C에서 열처리한 시편에서 얻어졌으며 (BH)$_{max}$는 214.6kJ.m$_{-3}$이다.

• Proceedings of the Korean Magnestics Society Conference
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• 2009.05a
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• pp.120-120
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• 2009

• Journal of KIISE:Software and Applications
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• v.37 no.10
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• pp.788-801
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• 2010

Advancing of mobile device is remarkable, so the research on mobile input device is getting more important issue. There are lots of input devices such as keypad, QWERTY keypad, touch and speech recognizer, but they are not as convenient as typical keyboard-based desktop input devices so input strings usually contain many typing errors. These input errors are not trouble with communication among person, but it has very critical problem with searching in database, such as dictionary and address book, we can not obtain correct results. Especially, Hangeul has more than 10,000 different characters because one Hangeul character is made by combination of consonants and vowels, frequency of error is higher than English. Generally, suffix tree is the most widely used data structure to deal with errors of query, but it is not enough for variety errors. In this paper, we propose fast approximate Korean word searching system, which allows variety typing errors. This system includes several algorithms for applying general approximate string searching to Hangeul. And we present profanity filters by using proposed system. This system filters over than 90% of coined profanities.